The present invention relates to a device for reducing the rotational speed of an ammunition unit and at the same time imparting a lateral speed to the ammunition unit.
Even if the invention can be used for all types of ammunition units for which a reduced rotational speed is desired, such as pyrotechnical ammunition, shaped-charge ammunition or the like, in the following the invention will be described in connection with submunitions, for example submunition units which are released from an aeronautical body, for instance a shell canister or the like, over a target area for searching this area in a helical pattern during the fall of the submunition towards the target area. Such submunitions are previously described in U.S. patent application Ser. No. 028,949.
In order to efficiently search a large target area it is necessary to limit the speed of fall towards the ground. Also a controlled rotational speed is necessary. The rotational speed must be high enough to make sure that the maximal interscan distance during the searching phase is less than the width of the target.
In case the submunition unit has no original rotational speed it is necessary to impart such a speed to the unit. In U.S. Pat. No. 4,356,770 a submunition unit is disclosed which has no original rotational speed but which is imparted such a speed by means of a breakable driving band which is fastened to the launching tube by one of its ends and partially surrounds the submunition unit.
On the other hand the rotational speed should not be too high for a desired wobbling, precession or helical motion to be maintained. For use in a modern artillery shell, for which the rotational speed amounts to more than 10,000 rpm, the rotational speed of the submunition device has to be reduced after separation from the shell body.
Prior art brake rotation devices for achieving a sensing motion are often of the parachute type, but devices using mechanical vanes are also previously known. In U.S. patent application Ser. No. 028,949 the submunition unit has a specific aerodynamical design so that a controlled rotational speed is obtained and the fall speed is limited.
In order to avoid interference between the searching areas of each submunition unit, and also to prevent a detonating submunition unit from disturbing other submunition units, the submunition units should have a specific distribution in the lateral direction. In some cases the lateral spread imparted to the submunition units due to the translational speed of the shell at the separation is enough. In other cases it is necessary to impart to the submunition unit a specific lateral movement. When the submunition units are released above the central part of a target area lateral movements in different directions should be imparted to the submunition units in order to cover as large a target area as possible.
For submunition units of the parachute type it is previously known to control the lateral speed to some extent by controlling the parachute. From DE-PS 33 23 685 it is previously known to control the lateral speed in order to increase the effect on a target area. By means of a motor the guide ropes of the parachute are actuated so that the submunition unit during its free trajectory moves in a desired direction. This is a complex system, however, and a comparatively large space in the shell canister is required which reduces the number of submunition units contained in the shell canister.